This invention relates to hydraulic door openers for manipulating swing doors or sliding doors or gates or other means for controlling traffic by vehicles or people through a passage way.
In many buildings and other structures it is often desirable to control passage ways for people or vehicles by doors or gates or other means which are manipulated by devices which for simplicity in this specification are generically called "hydraulic door openers". The space available for these devices is often restricted due to the door structure and since it is often desirable from architectural and other view points that the devices are neat and not cumbersome and can be placed more or less concealed in the structure. It is also important that the devices are reliable in function over a long time and easy to service when repair may be necessary.
A well-known device of the above type consists of an electric motor driven hydraulic pump which operates a hydraulic motor which in turn operates the door or gate in one direction of movement and tensions a spring whereas the spring operates the door or gate in opposite direction of movement, but said device is complicated and cumbersome and can easily get out of order. Other devices comprise linear hydraulic motors which make them still more cumbersome and often involves undesirable toothed rack structures.